Stress-induced Fos-like Immunoreactivity in the Pons and the Medulla Oblongata of Rats

Immunoreactivity of the immediate early gene c-fos was used to investigate changes in the activity of brainstem neurons in response to acute stressors like immobilization, formalin-induced pain, cold exposure, hemorrhage and insulin-induced hypoglycemia. Different stressors induced Fos-like immunoreactivity in different pontine and medullary neurons. A single, 3 hour immobilization was found to be a very strong stimulus that activated brainstem catecholaminergic (tyrosine hydroxylase-immunopositive) neurons and cells in the raphe and certain pontine tegmental nuclei, as well as in the reticular formation. Pain, induced by a subcutaneous injection of formalin was also effective on catecholamine-synthesizing neurons and on others cells in the nucleus of the solitary tract. Cold exposure activated cells mainly in the sensory spinal trigeminal and parabrachial nuclei and in the so-called "pontine thermoregulatory area". Moderate Fos-like immunoreactivity was induced by a hypotonic (25%) hemorrhage in medullary catecholaminergic neurons, the nucleus of the solitary tract and the Barrington nucleus. Among stressful stimuli used, insulin-induced hypoglycemia elicited the smallest Fos activation in the lower brainstem. The present observations indicate that different stressors may use different neuronal pathways in the central organization of the stress response.     

Measuring infant spatial working memory using a modified delayed-response procedure

Infant spatial working memory was assessed in 96 nine-month-old human infants using a modification of the delayed-response procedure. A person was the hidden stimulus, gaze was used as the response modality, the response context was a naturalistic "peek-a-boo" game, and a salient cue (i.e. curtains opening to reveal two windows) was used to evoke responses. Infants responded on most trials and performed significantly above chance in delay conditions of 10 and 20 seconds. Reinforcement affected performance, but performance was above chance even in a 0% reinforcement condition. These procedural variations boost estimates of infant spatial working memory over previous estimates and enhance the usefulness of the delayed-response procedure as a marker task for infant spatial working memory.     

Infant word segmentation and childhood vocabulary development: a longitudinal analysis

Infants begin to segment novel words from speech by 7.5 months, demonstrating an ability to track, encode and retrieve words in the context of larger units. Although it is presumed that word recognition at this stage is a prerequisite to constructing a vocabulary, the continuity between these stages of development has not yet been empirically demonstrated. The goal of the present study is to investigate whether infant word segmentation skills are indeed related to later lexical development. Two word segmentation tasks, varying in complexity, were administered in infancy and related to childhood outcome measures. Outcome measures consisted of age‐normed productive vocabulary percentiles and a measure of cognitive development. Results demonstrated a strong degree of association between infant word segmentation abilities at 7 months and productive vocabulary size at 24 months. In addition, outcome groups, as defined by median vocabulary size and growth trajectories at 24 months, showed distinct word segmentation abilities as infants. These findings provide the first prospective evidence supporting the predictive validity of infant word segmentation tasks and suggest that they are indeed associated with mature word knowledge. A video abstract of this article can be viewed at http://www.youtube.com/watch?v=jxzLi5oLZQ8 .     

Constructing a Mind,One Image Schema at a Time

In The Foundations of Mind, Jean Mandler describes how perceptual analysis provides a mechanism that allows infants to begin their journey into conceptual life, and subsequently to enter the advanced worlds of conceptual systems, memory, language, and consciousness. This review provides an overview of Mandler's theoretical position, celebrates her accomplishments, and supports the claim that The Foundations of Mind is a “must read” for all developmental scientists.     

Maternal perception of infant intentionality at 4 and 8 months

This study examines the degree to which mothers perceive infants as intentional and the relations among perception of intentionality, background variables, maternal emotional adjustment, and maternal interactive style. Forty mother-infant dyads were assessed when the infants were 4 months old, and 34 were retested at 8 months. Parent perception of infant intentionality (PPII) was measured via a rating of videotaped segments of infant behavior and an interview. Intentionality scores showed acceptable internal consistency and were positively intercorrelated at each age and across age. The two measures were aggregated to form an index of PPII at each age. Higher educational attainment was associated with lower PPII scores, experience with infants was associated with higher PPII scores, and academic knowledge about child development was not related to PPII. Mothers with more symptoms of anxiety had lower PPII scores, but high maternal separation anxiety was associated with higher PPII scores. Maternal symptoms of depression had a complex relation to PPII scores. Mothers rated as sensitive in mother-infant interactions had higher PPII scores. These variables accounted for 34% of the variance in PPII at 4 months and 49% at 8 months. There were also group differences: Mothers of 8-month-olds had higher PPII scores than mothers of 4-month-olds, mothers of girls had higher PPII scores than mothers of boys, and mothers attributed more intentionality in episodes with girls than in episodes with boys. The results are discussed in relation to mechanisms whereby PPII interacts with aspects of the parent and infant.     

A simple system for monitoring the timing of infant gaze to stimuli at specific locations

A system for monitoring the timing of infant gazes to specific locations is described. Infants sit on a parent’s lap in a dark room and observe videotaped stimuli presented on one of four monitors. Infrared (IR) light sources provide illumination for an IR-sensitive video camera and are positioned so that the infant’s direction of gaze can be readily apprehended on the basis of the reflections of the IR light sources relative to the infant’s pupil. The parent monitors the infant’s eyes through a headmounted display and keeps the infant in view of the video camera. Direction and timing of gaze shifts can be coded from frame-by-frame inspection of the videotape. We demonstrate that this coding is relatively accurate and that the present system provides some advantages over coding gaze direction on the basis of an unembellished video recording.     

The consequences of failing to imitate

Infants were shown three modeled acts presented in sequence. Imitation of one, two, or three of the modeled acts or failure to imitate was then observed. Distress was assessed prior to and following modeling. Infants who failed to imitate at least one act displayed a high level of distress. As a control, the same infants on another day observed the random manipulation of the stimuli. Distress failed to occur when the infants failed to imitate the scattering procedure. These results are discussed in terms of the child's development of internal standards. That is, during the latter part of the second year of life, infants show considerable distress when they fail to imitate coherent modeled acts. Since distress did not occur when the model simply scattered the stimuli, we assumed that interruption of play was not an incentive for distress. Deferred imitation was noted for older but not the younger cohorts.